Thermostatically controlled switch



Aug. 25, 1936. w, HODGMAN. JR 2,051,853

THERMOSTATI CALLY CONTROLLED SWITCH Filed NOV. 30, 1934 4 g \nvenTbr. M}: WiHis KHodgmon Jr. 49 46 47 43M by'M SZMMJ W Patented Aug. 25, 1936 PATENT OFFICE THEBMOSTATICALLY CONTROLLED SWITCH Willis K. Hodgman, Jr., Taunton, Mass.

Application November 30, 1934, Serial No. 755,279

8 Claims. This invention relates to an electric circuit closing device operated thermostatically.

The object of the invention is to provide such a device which shall act to close the circuit either upon the occurrence of a sudden or abnormal rise in temperature or upon the attainment of a predetermined temperature, and in which the closing of the circuit shall be effected with an abrupt movement to cause a quick and positive electrical connection.

The nature and objects of the invention will appear more fully from the accompanying description and drawing and will be particularly pointed out in the claims.

The drawing illustrates two preferred embodiments of the invention of a type Particularly designed for use as self-contained units in connecresponsive elements shown in Fig. 1.

tion with the operation of fire extinguishing or alarm-giving electrically controlled systems.

In the drawing: Fig. l is a front elevation of a unit embodying one preferred form of the invention.

Fig. 2 is a view in vertical cross section taken on the line 22 of Fig. l.

Fig. 3 is an end elevation of one of the thermo- Flg. 4 is' a detail in perspective of the guide arm and its supporting bracket shown in Figs. 1 and 2.

Fig. 5 is a view similar to Fig. 1 of a portion of the device with the parts in circuit closed position.

Fig. 6 is a front elevation of aiunit embodying a second preferred form of the invention.

Fig. 7 is a view in cross section taken on the line 'I'| of Fig. 6 and on a larger scale.

It isfrequently desirable in various electrically controlled systems, such, for example, as a sprinkler system installed for the extinguishment of a fire or, for example, as a system for giving an alarm, that means he provided which shall act to close the controlling electric circuit either when there is a sudden or abnormal rise in temperature or whena predetermined temperature has been reached. Such a devlce'is desirably in a compact, unitary form and a number of such units are installed at various points throughout the building or other place protected by or furnished with the System. It is of the highest importance that if one of these units acts, it shall eflect the closing of the circuit with absolute certainty, else the system cannot be depended upon and much of its value is lost. For example in the case of the well-known sprinkler systems installed in buildings for the automatic extinguish-' ment of fires, if a fire occurs in the vicinity of one ,of these units and either as the result of rapid combustion causes a sudden'rise in temperature or as the result of gradual combustion causes a predetermined temperature to be attained and the thermo-responsive unit fails to close the circuit, great damage may result. The same thing is true if the system is to function simply for givingan alarm. Infact, whatever may be the purpose of the system, that purpose will not be secured if the circuit is not promptly and surely closed. It must be remembered also that such systems usually stand inactive for long periods of time and only on rare occasions are required to function. Consequently the contacts or terminals which mustbe closed to render the system eifective become subject to more or less corrosion or other impairment.

The present invention has for its object to ensure that under the conditions set forth the closing of the circuit shall take place abruptly and with a quick, positive, and certain contact so that the effective operation of the system is ensured.

In that preferred embodiment of the invention shown in Figs. 1 to 5, inclusive, the device is of compact, unitary form employing a mercury.

switch controlled by two thermo-responsive elements and acting with an abrupt movement from open to closed circuit position to effect a quick 7 and positive closing electrical connection between bracket 4 secured thereto and, in the case illustrated, this bracket is shown secured by screws 5 to the ceiling 6 of the building. A shaft I extends transversely between the flanges 2 and 3 and is secured at each end thereto by nuts 8 threaded to the ends of the shaft. Upon this shaft are mounted two sleeves 9 and lo rotarily adjustable on the shaft and locked in adjusted position respectively by the set screws I iand II.

A thermo-responsive element I3 in the form of an open helix is secured at its inner end by the set screw l4 to'the sleeve 9. This element is in the form of a bimetallic strip with its two components having different coemcients of exit so that its forwardly projecting free end it rises and falls with the increase or decrease of temperature. These two ,thermo-responsive elements are similar except that It has a thermoresponsive movement slower than I! to a sudden rise in temperature but both of these elements respond with substantially equal increments of movement to a gradual rise in temperature. This functioning of the two thermo-responsive elements is best secured by making both of the same materials but with the one shown at It of greater mass. This is secured in the form illustrated by making the element It much thicker than the element It, as indicated by a comparison of Fig. 3 with the element shown in Fig. 2. It will thus be seen that these two thermo-responsive elements have a differential movement, the end It of the element It rising much faster than does the end It of the element It if the surrounding atmosphere has a sudden rise in temperature. This is due to the fact that owing to the greater mass of the element It, it responds more slowly than does the element II to a change in temperature. But these elements are readily so proportioned that if the surrounding atmosphere rises gradually in temperature, they will both respond with substantially equal increments of movement so that the ends it and It will rise and fall substantially uniformly. A mercury switch shown as an elongated hollow closed body I! of glass or suitable material containing a pool of mercury 10 is supported normally in an inclined position on the free ends l5 and ll of the thermo-responsive elements. Two wires 2| and 12 are shown extending from binding posts 23 mounted in the flange l and to which binding posts the arms of the electric circuit to be controlled may be secured. These wires extend into the interior of the body I! of the mercury switch and their free ends form two separated contacts which in this case constitute the terminals of the electric circuit and are maintained in a perfect and clean condition within the body It. In the normal position of the switch the contacts are in the elevated end of the switch with the pool of mercury 20 in the opposite depressed end.

The mercury switch is preferably held in position mounted and guided for bodily vertical movement and arranged to permit a pivotal or rocking movement. For this purpose a guide'arm construction shown separately in Fig. 4 is provided. This guide arm is of U-shape presenting the bifurcations 24 and I5 and at the base of the u has secured thereto a flanged portion 26 pivoted on the shaft 21 mounted in the bracket 28 secured to the flange 3. The mercury switch is pivotally mounted between and to the free ends of the bifurcations. This is conveniently secured by providing a saddle 28 in which the mercury switch rests and this saddle is pivoted at ill in the ends of the bifurcations 24 and 25. A depending arm 3| on the bifurcation 24 is provided with a point resting on the end ll of the theme-responsive element I, while a U-shaped element 31 is secured at 33 to the saddle 29 and provided with a point resting on the end I! of the thermo-responsive element It. The arc through which the pivot moves about the center 21 is comparatively flat and of short extent so that for all intents and purposes the mercury switch when moved bodily up and down moves in a substantially vertical path.

A set screw 34 constituting a limiting stop is threaded into and thus adjustably mounted in the base I directly over the end of the mercury switch and is locked in adjusted position by the lock nut 35.

The operation of the device will now be appar- I ent. Under normal conditions the parts stand in a position substantially as shown in Fig. 1 with the mercury switch supported on the free ends of the two thermo-responsive elements in an inclined position with the pool of mercuryat the end 10 opposite the contacts. If now a sudden rise in temperature of the surrounding atmosphere takes place, the thermo-responsive element It has a thermo-responsive movement much slower than l3. Consequently .while the free ends I! and ll 16 both rise to some extent, the end l5 rises more rapidly than the end it, with the result that the mercury switch is rocked on its pivot 30 and when a predetermined amount of this differential movement takes place and the mercury switch reaches 20 the horizontal, it is abruptly tipped into the opposite inclined position and the pool of mercury 20 is abruptly projected to the opposite end of the hollow body and in between the two contacts and effects a quick and positive electrical connec- 25 tion therewith, the parts assuming the position shown in Fig. 5. If, on the other hand, with the parts in the position shown in Fig. 1, a gradual rise in the temperature of the surrounding atmosphere takes place, the free ends 15 and II rise 30 with a joint movement responding with substantially equal increments of movement to the rise in temperature and the mercury switch moves vertically upward in the inclined position illustrated. But its upper end then comes in contact with the 35 set screw N and this set screw is so adjusted that when a predetermined temperature has been reached, the mercury switch is rocked by the joint upward movement of the supporting ends l5 and l8 coacting with the set screw 34 just past the 0 horizontal. Thereupon, as before, the mercury switch is abruptly tipped into the opposite inclined position and the pool of mercury III abruptly projected to the opposite end of the hollow body and in between the two contacts and eflects a quick 5 and positive electrical connection therewith.

Another embodiment of the invention is shown in Figs. 6 and '1 and serves further to illustrate the broad principles of the invention. In this device the two thermo-responsive elements 3 and 5 31 correspond to the thermo-responsive elements I! and It already described and are shown arranged and mounted in the same manner as. before. The rocking switch element is also shown as having a similar elongated hollow closed body It as in the case of the mercury switch and mounted, supported and guided in the same manner as that previously described. While a pool of mercury may be employed in this construction. there is herein shown in place thereof a spherical 00 weight 39. In this construction the electric contacts are mounted independently of the rocking member 38. The side flange 40 is shown as extended and offset at l I. On this flange is mounted a pair of contacts 42 and 43, both of which in this case are connected to a wire M which forms one terminal of the electric circuit. A bracket ll depends from the offset portion of the flange II and has pivotally mounted thereon at 46 a knife 41 adapted to enter between and have a sliding posi- 7 tive engagement with both of the contacts 42 and 43. In this case a wire 48 connected to the knife forms the other terminal of the electric circuit. The knife is projected into engagement with the contacts by a powerful spring 6! and is held in 15 aoanass 4 to havean abrupt movement being forced by the spring 49 quickly and positively into a sliding positive engagement with both of the contacts 42 and 43, thus effecting a positive electrical circuit closing connection.

It will thus be seen, as exemplified by the specific forms of the invention illustrated, that the pair of contacts may either constitute the two terminals of the electric circuit and the closing electric connection be eflected by the element projected therebetween or the pair of contacts may, one or both, constitute one terminal and the proiected element the other terminal, and the closing electric connection be effected by the projection of the elements therebetween. In any case, however, the action of the two thermo-responsive elements in response either to a sudden rise in temperature or in response to the attainment of a predetermined temperature is such as to effect an abrupt movement of the device from open circuit to closed circuit position and a quick and positive closing electrical connection with a pair of contacts thus ensuring with the highest degree of certainty the closing of the electric circuit and the functioning of the apparatus controlled thereby.

Having thus described the invention, what is claimed as new, and desired to be secured by Let ters Patent, is:

1. An electric circuit-closing device comprising a pair of contacts, means having an abrupt movement from open'circuit to closed circuit position and acting upon .such movement to effect a quick and positive closing electrical connection with said contacts, and two thermo-responsive elements, one of which has a theme-responsive movement slower than the other to a sudden rise in temperature and both of which respondwith substantially equal increments of movement to a gradual rise in temperature, the said thermoresponsive elements acting upon a predetermined amount of diifere'ntial movementin the former case and upon a predetermined amount of joint movement in the latter case to effect the abrupt closing movement of said means.

2. An electric circuit-closing device comprising a pair of contacts, an element having an abrupt movement from open circuit to closed circuit position and projected upon such movement in between the two contacts to eifect a quick and positive electric circuit closing connection, and two thermo-responsi've elements, one of which has a theme-responsive movement slower than H the other to a sudden rise in temperature and both of which respond with substantially equal increments of movement to a gradual rise in temperature, the said theme-responsive elements acting upon a predetermined amount of differential movement in the former case and upon a predetermined amount ofjoint movement in the latter case to eflect the abrupt closing movement of said element. I

3. An electric circuit-closing device comprising a pair of contacts, a pivotally mounted mercury switch having an abrupt rocking movement from open circuit to closed circuit position in which..

the mercury is projected upon said movement in between the two contacts to eifect a quick and positive electric connection therewith, and two thermo-responsive elements, one of which has a thermo-responsive movement slower than the other-to a sudden rise in temperature and both of which respond with substantially equal increments of movement to a gradual rise in temperature, the said thermo-responsive elements acting upon a predetermined amount of differential movement in the former case and upon a predetermined amount of joint movement in the latter case to effect the abrupt closing movement of said switch.

4. An electric circuit-closing device comprising a pair of contacts, a knife having an abrupt movement from open circuit to closed circuit position and forced upon said movement into a slid ing positive engagement with both of said contacts to efiect a positive electrical connection therewith, and two thermo-responsive elements, one of which has a thermo-responsive movement slower than the other to a sudden rise in temperature and both of which respond with substantially equal increments of movement to a gradual rise in temperature, the said thermoresponsive elements acting upon a predetermined amount of differential movement in the former case and upon a predetermined amount of joint movement in the latter case to effect the abrupt closing movement of said knife.

5. An electric circuit-closing device comprising a pair of contacts, a mercury switch having an elongated hollow body into one end of which the pair of contacts extends and which contains a pool of mercury, two thermo-responsive elements, one of which has a thermo-responsive movement slower than the other to a sudden rise in temperature and both of which respond with substantially equal increments of movement to a gradual rise in temperature, the said thermoresponsive elements normally supporting the mercury switch in an inclined position with the mercury at the end opposite the contacts and acting upon a predetermined amount of difierential movement in the former case and upon a predetermined amount of joint movement in the latter case to rock the switch past the horizontal and cause the mercury abruptly to be projected to the opposite end of the hollow body and in between the two contacts to effect a quick and positive electrieconnection therewith.

6. An electric circuit-closing device comprising the construction defined in claim 5, together with a guide arm mounted for vertical movement and pivotally connected to the mercury switch and acting to maintain the mercury switch in cooperative relation with the theme-responsive elements.

7. An electric circuit-closing device comprising a pair of contacts, a knife having an abrupt movement from open circuit to closed circuit position and forced upon said movement into a sliding positive engagement with both of said contacts to effect a positive electrical connection, a rocking switch having an elongated hollow body containing a weight movable abruptly from one end to the other of the body when rocked from an inclinedpositionpast the horizontal, two thermo-responsive elements, one of which has a thermo-responsive movement slower than the other to a sudden rise in temperature and both of which respond responsive elements rocking switch in an ing upon a. predetermined amount of differential movement in the former case end upon a predetermined amount of joint movement in the latter case to rock the switch past the horizontal and cause the weight to move abruptly to the opposite end of the switch, the said movement of the weight acting togive an abrupt further-rocking normally supporting the 10 movement to the switch and thereby eiiect the inclined position and act abrupt movement of the knife from open circuit to closed circuit position.

a. An electric circuit-closing device comprisingthe construction deflned in claim I, together with a. guide arm mounted for vertical movement and pivotally connected to the rocking switch and acting to maintain the rocking switch in coop erative relation with the memo-responsive elements.

WILLIS K. HODGM'AN, .71. 

